Subject: [mg123994] Re: Is this a bug in the Adjacency Matrix function? Using 8.9.4.0

From: Szabolcs <szhorvat at gmail.com>

Date: Wed, 4 Jan 2012 05:04:11 -0500 (EST)

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References: <jdulgc$jr3$1@smc.vnet.net>

Reply-to: comp.soft-sys.math.mathematica at googlegroups.com

On Tuesday, 3 January 2012 11:32:44 UTC+1, Richard Palmer wrote:
> testgraph=Graph[#[[1]]\[DirectedEdge]#[[2]]&/@{{1,3},{2,3},{3,4},{3,5},{4,6},{4,7},{5,7},{6,7}},
> VertexLabels->"Name",
> ImagePadding->10]
>
>
> MatrixForm[AdjacencyMatrix[testgraph],
> TableHeadings -> {Range[7], Range[7]}]
>
>
> The Adjacency Matrix appears to be incorrect, e.g. 1 is not adjacent to 2.
> What am I missing?
Writing an adjacency matrix assumes an ordering of vertices. In Mathematica this is not a simple lexicographic ordering, but the ordering is the same as that returned by VertexList.
The correct code to show the adjacency matrix is
MatrixForm[AdjacencyMatrix[testgraph],
TableHeadings -> {VertexList[testgraph], VertexList[testgraph]}]